The present invention relates to capping apparatus and more particularly to a capping device that is retrievable from high pressure oil wells once its well obstructing function is no longer needed.
The danger of an accidental explosion and accompanying combustion of combustible liquids and gases at oil and gas well sites has been recognized for many years. These explosions and resulting fires have occurred with some frequency ever since the first oil and natural gas wells were drilled. The problem has become particularly acute with the advent of drilling techniques which allowed deeper wells that tapped combustible fluids under greater pressure.
As a consequence of most of these explosions is the damage to the well head structures, including the valving necessary to control the fluid pressure and volume,
The above described problem has recently become suitable storage area. The above described problem has recently become acerbated by the intentional destruction of well heads by the use of explosives, in the middle East.
After careful consideration of the above-noted conditions, the inventor herein has developed a new and improved retrievable oil well capping device that may be lifted over and deposited in a high pressure well, and thereafter remotely controlled to temporarily completely obstruct the well casing without damage to the well in order to allow the well head structure to be repaired or replaced.
The inventor's new technique utilizes a radially expansive material that expands under axial compression in a manner that safely obstructs a well casing progressively from one end of the material to the other.
The prior art solutions to the above-noted problems have also been investigated. For example, in U.S. Pat. No. 546,258, there is disclosed a removable tube or pipe stopper disposable in Artesian or Driven Wells, including an upwardly-pointing cone fixed at the lower end of an interior hollow tube movably coaxially disposed within an exterior tube. An elastic sleeve is disposed over the exterior tube and held axially in place at the lower end of the tube by a collar. As a sleeve nut threadably engaged to the interior tube, at the upper end of the device, is rotated, the tube is drawn upwardly to force the cone into the bottom of the elastic sleeve. This forces the elastic material to engage the inner wall of the well to force any fluid flow to go through the tube that has a stop cock at its upper end.
U.S. Pat. No. 1,395,718 discloses an oil well packer that is placed in a well to be permanently capped and includes an elongated cylindrical body that is driven downwardly by impact on its cap to ratchet spring-loaded dogs downwardly along engaging teeth in an elongated bore of a sleeve at the bottom of the device. Just below the cap, and again lower in the unit, is an annular outwardly-pointing compressible member separated from an annular, generally inwardly-pointing compressible member, by an annular rigid disk. Therebelow, are alternately disposed annular outwardly-pointing rigid members and compressible member. Below the second compressible member is an inclined surface annular ridged wedge member that is separated from the lower wedge member by a rigid slip member.
As pounding continues on the cap, the dogs are ratcheted downwardly in the sleeve to lessen the distance between the upper edge of this sleeve and the inclined shoulder of the cap. This compresses the members to be forced inwardly against the body to form a seal, while the members are forced outwardly against the wall of the well.
U.S. Pat. No. 3,165,918 shows a well tool testing device adapted to be inserted into plastic-lined well pipe or the like to test the same for leaks by the application of a fluid under pressure. The tool has an external surface coated with a material which is softer than the plastic lining in the well pipe whereby accidental contact of the tool with the plastic lining of the well pipe does not abrade or scratch the same. The device is inserted into a well pipe. Rubber packer elements are positioned on opposite sides of the formed well joint to be tested and fluid under pressure is then caused to flow through a conduit into the testing device to cause the resilient packers to expand into sealing engagement with the well pipe and thereby seal off the section of well pipe to be tested. Pressure of the hydraulic fluid flowing into the testing device is then increased to the desired test pressure and the hydraulic test fluid flows into the sealed off section externally of the testing tool and applies this pressure to the well pipe.
U.S. Pat. No. 3,561,529 teaches a through-tubing non-retrievable bridge plug that includes telescoping tubing sections, with respectively decreasing diameters. Each such section has an equal length axially extending slot, and a second set of like slots. Each of these slots are staggered so that no two adjacent slots overlap. A central tubular section is disposed axially through the center of the bridge plug and extends beyond the upper and lower axial ends of the tubing sections. The lower end of the central tubular section is attached at its lower end to a valve housing, while, when the section is rotated first pulls the innermost section axially upwardly with respect to the outer sections, the slotted portions of the telescoping tubing sections are forced radially outwardly to engage and lock to the surrounding well structure.
U.S. Pat. No. 4,411,314 concerns a tool for insertion and retrieval of a casing packer, the packer having a body, slips 16 that hold the packer in place, packing gland of elastomeric material that seals the interior of a casing, and resilient drag springs that extend from the body to engage the interior of the casing. To set the packer, tubing is rotated to first radially extend the slips to engage the interior casing wall and lock it in place. Further rotation in the same direction causes the packing gland to expand outwardly to seal the interior of the casing.
From the foregoing it should be clear that none of the prior art techniques provide the expandable well casing sealing means of the invention which safely obstructs the well casing progressively along an elastomeric material from one end of the material to the other.
Thus, it should be recognized that a device that is relatively easily disposed over and into a very high pressure gushing oil well, even where the well head structure is somewhat damaged, and that safely and temporarily completely obstructs the well casing, would constitute an important advancement in the art.